Control system



Nov. 16, 1943. BROWN ETAL 2,334,537

' CONTROL SYSTEM Filed May 1, 1942 George M.Br*own, Claude M. Campbell,

Then Attorneg.

Patented Nov. 16, 1943 UNI-TED "STATES PATENT OFFICE coN'raor. SYSTEMGeorge M. Brown, Seotia, and Claude M. Campbell, Schenectady, N. Y.,aasignors to General Electric Company, a corporation of New YorkApplication May 1, 1942, Serial N0. 441,296

, 4 Claims. (01. 175-420) Our invention relates to systems for actuatingmovable elements such as switch or like elements adapted to be operatedto diflerent positions for the control of load or utilization circuitsor like uses, particularly to systems for operating movable elements orswitch means adapted for the remote control of circuits .in response tosignal frequencies, and its object is the provision of an improved andsimplified system of this character.

In accordance with our present invention this 7 object is attained byactuating a movable control element by a single electron dischargedevice, control electrode bias potentials of which are controlled, forexample, in response tothe resultant of potentials derived irom'signais,and cathode bias potentials of which are controlled in response tochange in the condition of the switchmeans, the control electrode biasmeans and the cathode bias means cooperating to cause the-electrondischarge device to open or to close the switch element or to maintainthis element in the position to'wh'lch it has been moved.

The novel features which are considered to be characteristic of ourinvention are set forth with particularity in the appended claims. Ourinvention itself, however, both as to its organization and method ofoperation together with further objects and advantages thereof may Illrespectively are connected in series two resist ances l3 and M. Therectiflers are shown herein as constituting a unitary rectifier devicein a single envelope but may be separate devices each having its ownenvelope. 4

The resistances l3 and H in series are connected across the inputcircuit of electron discharge device 4 to provide the biasing potentialfor the control electrode ii of the latterdevice, the electrode It beingconnected, in the present instance, through a filter resistor iito theouter terminal of the resistance II. The control elee-= trode I5 isconnected to ground or other suitable point of reierence potential ofthe system through afllter condenser ll. An initial positive bias isprovided for the cathode it of discharge device 4 by connection of thiscathode to a potentiometer comprising resistors 19 and 2t connectedacross the anode potential source. To

change the cathode :potential Irom its initial value, for a purpose tobe described hereinafter, the cathode I8 is adapted to be connected toground, or to a predetermined point of reference nofsignal is beingimpressed upon the input circharge device 4, shown herein as having thesame envelope as that of an electron discharge device 5.

The control electrode t of discharge device L5 is adapted to have signalpotentials impressed cuit or the latter. Therefore no bias potential isbeing impressed from the resistances l3 and I4 upon the controlelectrode l5 0! the electron discharge device i and the potential ofcontrol electrode I5 is at ground potential or at element or switch 2 toa second position, in the,

a present instance to close the switch, for examcircuits 1 and 8. Acrossthe rectifiers l and as pie, to initiate operation or the utilizationcircuit, an audio or tone signal at the resonant frequency of tunedcircuit 8 is impressed on the control I that appearing across circuit lt-since the imped ance of circuit 8, under this condition of signalfrequency, is greater than the impedance of circuit I. Rectification nowoccurs in rectifiers and I0, producing direct potentials acrossresistances I3 and 14 in proportion to the alternating voltages acrosscircuits 1 and 8. The rectiiiers are so connected that the directpotentials are in opposition. The resultant potential between thecontrol electrode l of device 4 and ground or point of referencepotential is thus the algebraic sum of the potentials across resistancesl3 and I4. Any alternating component in the potential impressed uponcontrol electrode I5 is removed by the filter constituted by resistancel6 and condenser I1.

When the potential across resistance I4 is thuscausedto exceed thatacross resistance Hi the resultant potential on the control electrode ofdischarge device 4 becomes positive with respect to ground or point ofreference potential and discharge device 4 becomes conductive. Anodecurrent then flows in energizing winding 3 of switch 2 causing thelatter ,to move from the open to the closed position, thereby closingcontacts l to initiate operation of any utilization circuit connectedthereto.

When switch 2 moves to the closed position as described, contacts 22close, thereby connecting cathode I8 of discharge device 4 to ground orpoint of reference potential through resistor 2|. The positive voltageon cathode i8 is thus reduced to such a value that upon termination ofthe signal of the frequency of circuit 8, and therefore of the positivevoltage impressed upon the control electrode IS, the discharge device 4remains conductive, The discharge device 4 thus potential appearingacross circuit 1 is now greater than that appearing across circuit 8since the impedance of circuit I, under this latter condition of signalfrequency, is greater than the impedance of circuit 8. The resultantpotential, produced after rectification as hereinbefore described,across resistances II and I4 in series is now negative with respect toground or reference potential and the negative resultant potentialimpressed upon the control electrode l5 of discharge device 4causes thelatter to become nonconductive. Anode current then ceases to flow inenergizing winding 3 of switch 2 permitting the latter to move fromtheclosed position bacl; to the open position, thereby opening contacts Ito terminate operation of the utilization circuit connected thereto andalso opening contacts 22 to permit subsequent re'closing of the switch.

Therefore, a short pulse of audio signal at a suitable predeterminedfrequency different from that of the first-named signal causes theswitch 2 to reopen and causes the system to remain in condition forreclosing of the switch means.

In a'practical example of an audio frequency control system inaccordance with our invention, a relatively low signal potential, of theorder of 0.5 volt,vat 1000 cycles per second was found to close theswitch means reliably and alike poten-.

tial at 235 cycles was similarly capable of reliably opening thecircuit. In the .practical system above mentioned, it was found thatfalse operation by random frequency signals, such as voice signals, wasvirtually impossible.

Our invention has been described herein in a particular embodiment forpurposes of illustration. It is to be understood, however, that theinvention is susceptible of various changes and modifications and thatby the appended claims we intend to cover any such modifications as fallwithin the true spirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. In combination, a movable element having an actuating winding, anelectron discharge device for energizing said winding, means for biasingthe cathode of said device positively to maintain saidwindingdeenergized, means for biasing the control electrode of saiddevice positively to energize saidwinding, means controlled by saidmovable element and operating simultaneously with said last-named meansfor reducing said positive cathode bias to maintain said windingenergized after said positive control electrode bias is removed, andmeans for biasing said control electrode negatively to deenergize saidwinding.

2. In combination, a movable element, an electron discharge device foroperation thereof having a cathode and a control electrode, means formaintaining said element in one position including means for causing thepotential of said cathode to become positive with respect to apredetermined initial potential of said control electrode, means foroperating said element to a second position including means for causingthe potential of said control electrode to become positive with respectto said predetermined initial potential, and means for maintaining saidelement in said second position after the potential of said controlelectrode returns to said initial potential, said last-named meansincluding means for causing the potential of said cathode to become lesspositive with respect to the potential of said control electrode.

3. In combination, a movable element, an electron discharge device foroperation thereof having a cathode and a control electrode, means formaintaining said element in one position including means for biasingsaid cathode positively with respect to a predetermined referencepotential and means for maintaining the potential of said controlelectrode at said reference potential, means for operating said elementto a second position including means for biasing said control electrodepositively with respect to said reference potential, and means formaintaining said element in said second position after the potential ofsaid control electrode is returned to said reference potential, saidlast-named means including means for causing the biasing potential ofsaid cathode to become less positlvewith respect to said referencepotential.

4. In combination, a movable element, an electron discharge device foroperation thereof to a plurality of positions corresponding toprearranged signals and having a cathode and a conreference potential inthe absence of said signals.

means for operating said element to a second position includingmeansresponsive to one of said signals for biasing said control electrodepositively with respect to said reference potential, means formaintaining said element in said second position after said one of saidsignals is discontinued and the potential of said control electrode isreturned to said reference potential said control electrode negativelywith respect to said reference potential.

GEORGE M. BROWN. GLAUDE M. CAMPBELL.

